This study examined both the behavioral performance and the brain mechanisms of post-error adjustments under long-term psychological stress by using ERP technique. Forty two participants who had been exposed to long-term exam preparation (versus 21 controls who were not exposed to such exam) performed a Go/NoGo task while electroencephalograms were recorded. We used Cohen's Perceived Stress Scale to assess their chronic stress level, and results suggested that participants in the exam group had higher levels of perceived stress. Although the behavioral performance of post-error trials had no difference between two groups, the exam group elicited significantly decreased P3 amplitude than the non-exam group in the post-error condition. Furthermore, the P3 amplitude in the post-error condition was negatively correlated with the perceived stress scores, suggesting that long-term psychosocial stress may lead to the decrease of the attention resource after committing an error.